Rotary presses serve for the manufacture of tablets above all, in the pharmaceutical field for instance. However, they can be used everywhere where articles pressed from powder material are desired, for instance in the field of candies and foodstuffs, for washing agents and so on.
The basic construction of a rotary press is always the same. It has a rotor, which is driven around a vertical axis by a suitable drive motor. The rotor contains an upper and a lower punch guide, which receive upper and lower punches, respectively. The punches co-operate with bores of a die plate, which is arranged between the punch guides. Material which is to be compressed is supplied to the die bores, and heads of the upper and lower punches, respectively, co-operate with compression rollers in compression stations in order to press the compression material in the die bores together. The compression material is fed into the die bores via a suitable filling station. Outside of the compression stations, the punch heads are guided by suitable radial cam sections. For instance, a radial filling cam section is associated to the filling station, which provides that the lower punches project into the die bores for a preset extent in the region of the filling station. This extent determines the filling volume, and with this also the weight of the pressed tablet. In the strip-off region, in which the compressed tablets are stripped off from the upper side of the die plate, a radial cam provides that the lower punches are lifted so far that the pressed articles can be captured and shoved off by the stripping device. Furthermore, a corresponding radial cam section provides for the upper punches that sufficient space remains for the filling station for filling in compression material again.
Such a rotary press is commonly known. For instance, it is made reference to DE 10 2004 040 163 A1, the entire contents of which is incorporated herein by reference.
It is further known to form single layer or multilayer compressed articles with the described rotary press. For the single layer compressed article, one filling- and dosage station and one pre-compression and one main compression station are usually provided, each at a time with an upper and a lower compression roller. In a rotary press for producing two-layer tablets, only one compression station is usually used for the compression of the first layer. Subsequently, the material for the second layer is filled in with the aid of a second filling- and dosage station. The definite pressing together of the two layers takes then place by a pre-compression station and a main compression station. When three or more layers are formed into a tablet, the sequential arrangement of filling- and dosage stations and compression stations is correspondingly continued.
However, it is also known to increase the production capacity with single layer pressed articles in that two or more filling- and dosage stations are provided, to each one of which at least one compression station is arranged downstream. In this way, the production capacity can be doubled or multiplied at equal rotational speed of the rotary press.
The user of a rotary press decides which kind of rotary press is necessary or optimum for his/her production. When he/she produces single layer tablets in small batches, he/she will chose a relatively small rotary press, which has only one filling- and dosage station and two compression stations. When he/she desires to produce greater batches, according to the conditions he/she will prefer a rotary press which has two filling- and dosage stations, each one with two compression stations at a time. With such a rotary press, even a double layer tablet can be produced, when it is suitably remodelled. When the user desires to produce very large batches or three-layer tablets, he/she will provide three filling- and dosage stations, each one with two compression stations at a time. For each one of the described kinds of rotary presses, the stand has to be dimensioned correspondingly, and the press manufacturer has to provide different construction series for the rotary presses in order to fulfil the different user requirements.
The present invention is based on the objective to provide a rotary press which fulfils the different user requirements with a minimal expenditure of production and which can be remodelled to another usage form with little expense, even retroactively.